Outline

1
Ongoing Research in Communication Technology
Laboratory
Information Engineering Department The Chinese
University of Hong Kong
Prof. Tak-Shing Peter Yum (??? ??)
2
Outline

• Internet
• Congestion Control (Cun-Qing Hua)
• Peer-to-Peer Network (Li Zhang)
• Internet Content Adaptation Protocol (Wing-Lam
  Tam)
• Wireless Communication
• OVSF Code Assignment Schemes (Yang Yang)
• Cell Sectoring for CDMA Systems (Fang-Zhong Shen)
• Routing
• Offline Routing for RPR (Cheng Li)

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Congestion Control 1

• Host-based Congestion Control
• Based on packet loss detection
• e.g. TCP Tahoe, Reno and NewReno
• Based on end-to-end delay variance
• e.g. TCP Vegas and Tri-S
• Advantages
• Easy to implement
• Easy for decentralized resource allocation
• Weakness
• long response delay (at least one round trip
  time)
• Limited information collected solely from end
  hosts may lead to improper response to congestion

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Congestion Control 2

• Case study TCP Vegas
• The TCP Vegas flows passing through multiple
  congested links tend to be unfairly treated due
  to the cumulative nature of round trip time
• Router-based Congestion Control
• Routers monitor the network state and notify the
  end hosts in case of congestion by dropping or
  marking packets e.g. RED, BLUE, ECN

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Congestion Control 3

• Our solutionThe Joint Congestion Control (JCC)
• It unifies the efforts of end hosts and routers
  to provide proactive and accurate congestion
  control
• Basic Idea
• The source sends probing packets to collect the
  state of the most congested link along the path,
  and with which to adjust the congestion window
• Properties
• Lower variance of throughput
• Lower packet loss rate
• Fairer resource allocation

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Peer-to-Peer Network 1

• Traditional C/S Model
• P2P network
• every node can take the roles of both server and
  client
• intermittently connected edge devices (PC, PDA,
  WAP Phones) can receive information from and
  provide information to the Internet
• Takes advantage of edge device resources
• Storage and processing capability of edge devices
• Content of edge devices
• Human presence at edge devices

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Peer-to-Peer Network 2

• Typical Problems
• A distributed naming scheme for nodes and files
• A distributed file indexing scheme
• Server selection
• A distributed routing protocol (reverse anycast)
• Security and authentication

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Peer-to-Peer Network 3

• Our work
• Architecture and topology
• Architecture design Distributed, Centralized and
  Augmented
• Network partitioning
• Server selection
• Network distance Measures
• Routing rules
• Delay and throughput Analysis

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OVSF Code Assignment Schemes 1

• Orthogonal variable-spreading-factor(OVSF) codes
  are the basic resource units for assignment in
  UTRA-TDD and FDD systems

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OVSF Code Assignment Schemes 2

• Nonrearrangeable and rearrangeable code
  assignment schemes
• Our solution Compact Assignment (CA) and
  Rearrangeable Compact Assignment (RCA)
• Both schemes can leave the resulting code tree as
  flexible as possible (in supporting multi-rate
  traffic classes) after each code assignment
• Analytical and simulation results show both
  schemes can offer the blocking, throughput and
  fairness performance very close to the
  theoretical bounds
• Compared with other schemes, CA and RCA have the
  combined advantage of simple, efficient, stable
  and fair
• Generalization optimize the assignment to match
  the traffic rate distribution

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Cell Sectoring for CDMA Systems 1

• Problem
• Cell sectoring is used to reduce the co-channel
  interference
• However, it works inefficiently when addressing
  hot-spot scenarios. Some congested sectors may
  have outages, while the lightly loaded sectors
  may have spare capacity
• Solution
• Dynamic cell sectoring, i.e., adaptively changing
  the sector pattern according to the traffic can
  solve the problem

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Cell Sectoring for CDMA Systems 2

• Three Aspects
• How to produce dynamic sector patterns?
• Circular Array Beamforming networks with Butler
  Matrix
• Dynamic Cell Sectoring Algorithms
• MinTTP Sectoring based on Shortest Path Algorithm
• PE Sectoring based on Greedy Algorithm
• How to keep the optimality of the sectoring at
  all times
• Resectoring Detect the traffic and readjust the
  sector boundaries when necessary.

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Internet Content Adaptation Protocol 1

• Objective
• Develop Web services for customizing content
• Language Translation
• Advertisement Insertion
• Conventional Approach
• Proprietary API
• Single-source solution, creating programming and
  testing complexities
• Problems of scalability, flexibility, reusability

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Internet Content Adaptation Protocol 2

• Our Approach
• Attach application servers to proxies through
  ICAP

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Internet Content Adaptation Protocol 3

• Internet Content Adaptation Protocol
• Open protocol
• Enables communication between edge content
  devices (web caches and Internet content origin
  servers) and application servers for content
  adaptation
• Part of an evolving architecture that promotes
  Web scalability by better facilitating
  distribution and caching

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Internet Content Adaptation Protocol 4

• Work Involved
• Development of the ICAP protocol core
• Architecture design
• Software implementation
• Development of the ICAP-enabled e-services
• Content filter and transcoder for WAP phones
• Advertisement insertion server
• Performance analysis of ICAP-enabled proxy
• ICAP overhead
• System scalability, efficiency
• Caching performance

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Offline Routing for RPR 1

• The topology of IEEE 802.17 Resilient Packet Ring
  (RPR) is as follows

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Offline Routing for RPR 2

• Objective
• Design the link capacity dimensioning for this
  system
• Problems
• Given Traffic matrix, Ring topology, utility
  function
• Maximize the system revenue or throughput while
  maintain fairness among the competing flows
• Given Traffic matrix, utility function
• Link capacity dimensioning
• Solutions
• Linear programming
• Non-linear programming with convex objective
  function and linear constraints